Herbicides test method

ABSTRACT

An isolated DNA molecule encoding a protein from a plant, which protein has pantothenate synthetase activity; a non-naturally occuring chimeric gene comprising a promoter operably linked to a DNA molecule encoding a protein from a plant having pantothenate synthetase activity; a recombinant vector comprising the chimeric gene wherein the vector is capable of being stably transformed into host cell, a host cell stably transformed with a vector wherein the host cell is capable of expressing the DNA molecule; a method for assaying a protein having pantothenate synthetase activity; the use as herbicides of compounds which inhibit pantothenate synthetase, and a herbicidal composition, comprising one or more active ingredients which show significant pantothenate synthetase inhibition in an assay, are disclosed.

[0001] The invention relates to plant enzymatic activity, and aspects thereof, involved in the biosynthesis of Coenzyme A. The invention particularly relates to the plant enzyme known either as pantoateo-β-alanine ligase (EC 6.3.2.1), pantoate activating enzyme or pantothenate synthetase (PS). PS catalyses the synthesis of pantothenate.

[0002] PS is an essential enzyme in the in planta biosynthesis of the vitamin and Coenzyme A precursor pantothenate. It is known to catalyse the following reaction:

ATP+(R)-pantoate+β-alanine→AMP+pyrophosphate+(R)-pantothenate.

[0003] PS genes have previously been isolated from Escherichia coli (GenBank accession number P31663), Bacillus subtilis (GenBank accession number P52998), and the cyanobacterium Synechocystis (GenBank accession number U44896). DNA sequences from Saccharomyces cerevisiae (GenBank accession number P40459) and Schizosaccharomyces pombe (GenBank accession number Q09673) having unknown functions have been proposed to code for PS enzymes based on DNA and deduced amino acid sequence similarities. To date, however, no gene has been reported which codes for the PS enzyme in any plant species. It is therefore an object of the invention to identify, isolate and sequence a gene coding for the PS enzyme present in plants.

[0004] A number of assays have been reported for measuring PS activity. One assay developed by Maas (1950a and 1950b) uses a microbiological assay of pantothenate based on the ability to promote growth of an E. coli pantothenate auxotroph (M99-1, panC). The assay developed by Pfleiderer et al (1960) measures the AMP liberated in the PS reaction. In this assay, myokinase catalyses the production of 2 moles of ADP for each mole of AMP released in pantothenate synthesis using ATP supplied in the assay mixture. Pyruvate kinase then generates 2 moles of pyruvate and ATP for 2 moles of phosphoenolpyruvate and ADP. Finally, lactate dehydrogenase reduces 2 moles of pyruvate to yield 2 moles of lactate concomitant with stoichiometric oxidation of NADH to NAD, which can be monitored spectrophotometrically by following the absorbance at 340 nm. A third assay, developed by Miyatake et al (1979), employs an assay mix containing ¹⁴C-β-alanine and unlabelled pantoate. In this assay any ¹⁴C-pantothenate formed is separated from unreacted ¹⁴C-β-alanine by cation exchange chromatography and subsequently quantified by liquid scintillation counting. These assays, however, are not suitable for use with high throughput biochemical screening and cannot be used for the large scale biochemical screening of compounds necessary to discover useful inhibitors of PS.

[0005] We have developed an invention which addresses the above-mentioned drawbacks associated with the prior art. Our invention covers a number of related aspects which encompass the same inventive concept.

[0006] According to a first aspect of the invention there is provided an isolated DNA molecule encoding a protein from a plant, which protein has PS activity. In preferred embodiments, the DNA is isolated from Lotus japonicus or Oryza sativa.

[0007] To support our invention we herein disclose the cDNA sequence from Lotus japonicus. In addition, we have shown that a previously unassigned expressed sequence tag of Oryza sativa (GenBank accession number D25017) is part of a cDNA coding sequence for a PS enzyme in Oryza sativa and disclose, as part of this invention, the full cDNA sequence of the PS gene from Oryza sativa. Furthermore, we have confirmed by sequence similarity, functional complementatibn of an Escherichia coli mutant devoid of PS enzyme activity, and by enzyme assays that the DNA sequence from Saccharomyces cerevisiae (GenBank accession number P40459) putatively ascribed as coding for a PS enzyme does code for the PS enzyme of Saccharomyces cerevisiae. A cDNA sequence coding for a PS enzyme in Lotus japonicus is provided in FIG. 1.2. A cDNA sequence coding for a PS enzyme in Oryza sativa is provided in FIG. 2.2. A DNA sequence coding for a PS enzyme in Saccharomyces cerevisiae is provided in FIG. 3.3. As a result of our invention it is now possible to obtain the DNA coding sequence for the PS, enzyme(s) from any plant source using methods available to those skilled in the art.

[0008] A further preferred embodiment of this aspect of our invention is an isolated DNA molecule encoding a protein from Lotus japonicus having PS activity wherein said protein comprises the amino acid sequence set forth in FIG. 1.2. A still further embodiment is an isolated DNA molecule encoding a protein from Oryza sativa having PS activity wherein said protein comprises the amino acid sequence in FIG. 2.2.

[0009] In addition, we have extended our invention to include a further aspect so as to provide a non-naturally occurring chimeric gene comprising a promoter operably linked to a DNA molecule encoding a protein from a plant having PS activity. Preferably, the protein is isolated from a dicotyledonous or a monocotyledonous plant, such as Lotus japonicus or Oryza sativa. Preferably the amino acid sequence is selected from the group, set forth in FIG. 1.2 (Lotus japonicus) and FIG. 2.2 (Oryza sativa).

[0010] We have developed our invention into another aspect which provides a recombinant vector comprising a chimeric gene, wherein the vector is capable of being stably transformed into a host cell. Also comprised in this aspect is the host cell stably transformed with the vector wherein the host cell is preferably a cell selected from the group consisting of a bacterial cell, a yeast cell, and an insect cell and is further capable of expressing the DNA molecule according to the invention.

[0011] In a still further aspect we have applied our invention to the recombinant production of the PS enzyme. In particular, the invention provides a method of producing a protein having PS activity in a host organism by firstly inserting a DNA sequence encoding a protein having PS activity into an expression cassette designed for the chosen host; inserting the resultant molecule, containing the individual elements linked in proper reading frame into a vector capable of being transformed into the host cell; growing the thus transformed host cell in a suitable culture medium; and isolating the protein product either from the transformed cell or the culture medium, or both, and purifying it.

[0012] In addition, we have developed our invention to provide methods for assaying a protein having pantothenate synthetase activity comprising; incubating pantothenate synthetase in a suitable reaction mixture in which pantothenate synthetase is capable of catalysing the conversion of pantoate, □-alanine and ATP to pantothenate, AMP and pyrophosphate; determining the amount of pyrophosphate formed by a calorimetric technique based on the assay for pyrophosphate developed by Chang et al. (1983); or converting the pyrophosphate formed by the catalytic activity of the pantothenate synthetase into inorganic phosphate by the catalytic activity of an inorganic pyrophosphatase, preferably yeast inorganic pyrophosphatase; and determining the amount of inorganic phosphate generated by the catalytic activity of said inorganic pyrophosphatase by colorimetric techniques, preferably by techniques based either on the assay for inorganic phosphate developed by Lanzetta et al. (1979) or on the assay for inorganic phosphate developed by Chifflet et al. (1988).

[0013] The production of PS, for example by using the recombinant methodology described hereinabove, has enabled us to develop methods of using purified PS to screen for novel inhibitors of PS activity which may be used as herbicides to control undesirable vegetation in fields where crops are grown, particularly agronomically important crops such as maize and other cereal crops such as wheat, oats, rye, sorghum, rice, barley, millet, turf and forage grasses, and the like, as well as cotton sugar cane, sugar beet, oilseed rape, and soybeans.

[0014] In particular, the present invention relates to a method for assaying a chemical entity for the ability to inhibit the activity of a PS enzyme from a plant by:

[0015] a) combining said PS enzyme in a suitable reaction mixture in which

[0016] i) said PS enzyme is capable of catalysing the conversion of pantoate, β-alanine and ATP to pantothenate, AMP and pyrophosphate;

[0017] ii) the pyrophosphate liberated in the PS reaction is determined by a calorimetric method, preferably by a method based on the assay for pyrophosphate developed by Chang et al. (1983);

[0018] iii) or the pyrophosphate liberated in the PS reaction is further converted to inorganic phosphate by the catalytic activity of an inorganic pyrophosphatase, preferably yeast inorganic pyrophosphatase; and

[0019] iv) the inorganic phosphate generated by the catalytic activity of inorganic pyrophosphatase is determined by a calorimetric method, preferably by a method based on the assay for inorganic phosphate developed by Lanzetta et al. (1979) or by a method based on the assay for inorganic phosphate developed by Chifflet et al. (1983);

[0020] b) combining said chemical and said PS enzyme together in a second reaction mixture under the same conditions as in said first reaction mixture; and

[0021] c) measuring the amount of pyrophosphate or inorganic phosphate produced in said first and said—second reaction mixture;

[0022] wherein said chemical is capable of inhibiting the activity of said PS enzyme if the amount of pyrophosphate or inorganic phosphate measured in said second reaction mixture is significantly less than the amount of pyrophosphate or in organic phosphate measured in said first reaction mixture.

[0023] The assay principle invented here is not limited to measuring PS activity but can be employed to measure any enzyme whose catalytic activity involves the formation of a substrate-nucleotidyl reaction intermediate by transfer of the nucleotidyl moiety from the corresponding nucleoside triphosphate to a suitable substrate, thereby generating inorganic pyrophosphate as one reaction product. Such enzymes include, but are not limited to, all aminoacyl-tRNA synthetases, asparagine synthetase, acetate thiokinase, dephosphocoenzyme-A-pyrophosphorylase and all enzymes catalysing the formation of nucleotide diphosphate sugars. The assays are preferably carried out on a microtiter scale and are preferably employed for the high-throughput biochemical screening of inhibitors of the enzymes.

[0024] The present invention is further directed to probes capable of specifically hybridising to a plant PS gene, cDNA or mRNA, wherein the probe comprises a contiguous portion of the coding sequence for a PS enzyme from a plant at least 10 nucleotides in length.

[0025] A further aspect the invention provides a method of producing a DNA molecule comprising a DNA portion encoding a protein having PS activity by,

[0026] a) preparing a nucleotide probe capable of specifically hybridising to a plant PS gene, cDNA or mRNA, wherein the probe comprises a contiguous portion of the coding sequence for a PS enzyme from a plant at least 10 nucleotides in length;

[0027] b) probing for other PS coding sequences in populations of cloned genomic DNA fragments or cDNA fragments from a chosen organism using the nucleotide probe prepared according to step a); and

[0028] c) isolating a DNA molecule comprising a DNA portion encoding a protein having PS activity.

[0029] DNA encoding the PS enzyme may be isolated from any desired plant species according to the invention. One method taught for isolating a plant PS coding sequence is represented by Example 1. In this method cDNA clones encoding a PS enzyme are identified from a library of cDNA clones derived from the plant of interest based on their ability to supply PS enzymatic activity to a mutant host organism deficient in this activity. Suitable host organisms for use in this method are those which can be used to screen cDNA expression libraries and for which mutants deficient in PS activity are either available or can be routinely generated. Such host organisms include, but are not limited to, E coli panC (strain AT1371).

[0030] Alternatively, plant PS coding sequences may be isolated according to well known techniques based on their sequence homology to the Lotus japonicus PS coding sequence set forth in FIG. 1.2 or to the Oryza sativa PS coding sequence set forth in FIG. 2.2. In these techniques all or part of the known PS coding sequence is used as a probe which selectively hybridises to other PS coding sequences present in populations of cloned genomic DNA fragments or cDNA fragments (i.e. genomic or cDNA libraries) from a chosen organism. Such state of the art techniques include hybridisation screening of plated DNA libraries and amplification by PCR using oligonucleotide primers corresponding to sequences conserved among known PS amino acid sequences.

[0031] For recombinant production of the PS enzyme in a host organism, the plant PS coding sequence may be inserted into an expression cassette designed for the chosen host and introduced into, the host where it is recombinantly produced. The choice of specific regulatory sequences such as promoter, signal sequence, 5′ and 3′ untranslated sequences, and enhancer appropriate for the chosen host is within the level of skill of those skilled in the art. The resultant molecule, containing the individual elements linked in proper reading frame, may be inserted into a vector capable of being transformed into the host cell. Suitable expression vectors and methods for recombinant production of proteins are well known for host organisms such as E. coli, yeast and insect cells. Specific examples include plasmids such as pBLUESCRIPT, pFLAG, pTrcHis, and baculovirus expression vectors, for example those derived from the genome of Autographica californica nuclear polyhedrus virus.

[0032] Recombinantly produced plant PS can be isolated and purified using a variety of standard techniques. The actual techniques which may be used will vary depending upon the host organism used, whether the PS enzyme is designed for secretion, and other such factors familiar to those skilled in the art.

[0033] Recombinantly produced plant PS is useful for a variety of purposes. For example, it may be used in an in vitro assay to screen known herbicidal chemicals whose target has not been identified to determine if they inhibit PS. Such an in vitro assay may also be used as a more general screen to identify chemicals which inhibit PS activity and which are therefore herbicide candidates. Alternatively, recombinantly produced plant PS may be used to elucidate the complex structure of this enzyme. Such information regarding the structure of the PS enzyme may be used, for example, in the rational design of new inhibitory herbicides.

[0034] Typically, the inhibitory effect on PS is determined by a significant reduction, a reduction that is greater than the margin of error inherent in the measurement technique, of pantothenate synthesis in the in vitro assay. Such a determination may be made simply by comparing the amount of pantothenate synthesised in the in vitro assay in the presence and absence of the candidate inhibitor.

[0035] The disclosures in British patent applications 97 11.1 63.7 and 97 134 77.9 from which this application claims priority, and in the abstract accompanying this application are incorporated herein by reference.

[0036] The invention will be further described by reference to the following detailed examples. These examples are provided for purposes of illustration only, and are not intended to be limiting unless otherwise specified.

EXAMPLES

[0037] A number of standard techniques have been used during development of our invention. These includes: cloning of plant genes by functional complementation (for example Senecoff and Meagher, 1993); the use of inverse PCR to recover fragments of genes not present in conventional libraries (Ocham et al, 1989) and the use of DNA sequence databases to discover PS genes cloned from other species which had unknown function at the time of their submission.

Example 1

[0038] Isolation of a cDNA Clone Encoding Pantothenate Synthetase from Lotus japonicus

[0039] A L. japonicus PS clone was isolated by functional complementation of E. coli AT1371 (panC4, Δ(gpt-proA)62, lacY1, tsx-29, glnV44(AS), galK2, λ⁻, rac-0, hisG4(Oc), rfbD1, xylA5, mtl-1, argE3(Oc), thi-1, described by Cronan et al., 1982) from a cDNA library (from Corinna Tetzlaff, Department of Plant Sciences, University of Cambridge, Downing Street, Cambridge, C823EA, UK) The PS cDNA was found in a population of 50,000 ampicillin-resistant transformants of E. coli AT1371. The PS clone (pLC), was subcloned and sequenced as summarised in FIG. 1.1. The resulting nucleotide sequence (FIG. 1.2) revealed the presence of an open reading frame (ORF) encoding a polypeptide of 308 residues which is 61% similar to the protein sequence of PS from E coli. The open reading frame of PS was in frame with the lacZ on the pBLUESCRIPT vector which probably accounts for the expression of L. japonicus PS and hence complementation of E. coli AT1371.

Example 2

[0040] Isolation of a cDNA Clone Encoding Pantothenate Synthetase from Oryza sativa

[0041] A PS cDNA sequence from rice was found by nucleotide database searches as an expressed sequence tag (EST) of rice that had been submitted to GenBank (accession number D25017) on behalf of the Japanese Rice Genome Research Program. The full corresponding cDNA clone was obtained from Dr. Yuzo Minobe, National Institute of Agrobiological Resources, Kannondai, Tsukuba Ibaraki, Japan. This cDNA clone was called pRC1 and subcloned and sequenced as shown in FIG. 2.1. The nucleotide sequence of the 1.3 kb SalI-NotI insert of pRC1 and the predicted amino acid sequence of the PS gene are given in FIG. 2.2. When this sequence was compared to other PS sequences, the similarity originally seen within the 5′ EST region held for the entire open reading frame implying that the rice cDNA in pRC1 does code for PS. However, pRC1 did not complement the E. coli panC mutant. Thus, a fusion clone of lacZ and rice PS gene was derived from pRC2 (FIG. 2.3) that allowed both transcription of the rice cDNA and translation of the protein as a β-galactosidase fusion. Complementation of the E. coli panC mutant with the rice pantothenate synthase gene was achieved using this fusion one.

Example 3

[0042] Comparison of the Amino Acid Sequences of Known, or Predicted to be, Pantothenate Sythetases

[0043] When the amino acid sequences of known, or predicted to be, pantothenate-sythetases were aligned (FIG. 3.1), the putative PS protein sequences of Saccharomyces cerevisiae and Schizosaccharomyces pombe showed significant homology with E. coli PS. To confirm that the putative PS gene Of Saccharomyces cerevisiae did code for an enzyme with PS activity, a phage clone (PM4950) containing a 20 kb genomic fragment of the yeast chromosome IX which spans the putative PS gene was obtained from Dr. Carol Churcher, Sanger Centre, Hinxton Hall, Cambridge, UK. The open reading frame coding for the putative gene was subcloned in two steps for expression in E. coli as shown in FIG. 3.2. In the resulting plasmid, pYC1, the yeast PS gene was under transcriptional control of the lacZ promoter. However, PS was not in frame with lacZ and therefore was not expressed as a fusion protein. The nucleotide sequence and putative translation product of the 1.5 kb EcoRV-HindIII gnomic fragment in pYC1 are given in FIG. 3.3. Yeast PS functionally complemented the panC lesion in E coli AT1371, confirming that the gene did code for a functional PS.

Example 4

[0044] Isolation of the 5′ and the 3′ Ends of Pantothenate Synthetase from Lotus japonicus

[0045] We expected plant PS to be located in the chloroplast, but there was no evidence from the PS cDNA clones of L. japonicus and O. saliva of any chloroplast transit signals. Furthermore, both enzymes were predicted to be cytosolic proteins by pSORT (Molecular Biology Tools, ExPasy WWW Server).

[0046] To clone 5′ and 3′ sequences of the PS gene inverse PCR (iPCR) was used. Genomic DNA was isolated from L. japonicus leaf tissue and prepared as described by Dellaporta et al (1983). Aliquots of Lotus genomic DNA (8 μg) were digested overnight with the following restriction endonucleases: BamHI, EcoRI, HindIII, NotI, SalI, XbaI, XhoI. DNA fragments were precipitated with isopropanol and resuspended in TE buffer before loading onto an agarose gel. After electrophoresis, gel pieces corresponding to fragment sizes of between 2 kb and 15 kb were isolated from the agarose gel, and purified using the US BioClean MP kit (United States Biochemical, Cleveland, Ohio, USA). Each reaction was ligated overnight at 14° C. with 1.5 units of T4 DNA ligase in conditions which promote intra-molecular ligation. DNA was precipitated from the ligation mix with isopropanol, washed with ethanol, resuspended in sterile distilled water and used as templates in the following PCR step.

[0047] PCR amplification was carried out using the Expand High Fidelity PCR system from Boehringer Mannheim, FRG, adopting the manufacturers protocol for amplification of DNA of a size of up to 3 kb. The design of L. japonicus PS-specific primers Li5 and Li3 (Li5: dCGGGATCCATGGTGGGACGAGGGCGATGAG and Li3: dCATCAAGCTTATGTATCAAAGTGCCCCAGG) followed the general protocols for iPCR by Ochman et al. (1989). Restriction sites incorporated into the Li primers are HindIII in Li3 and BamHI in Li5 (underlined). Of all seven templates only the BamHI-derived circular Lotus library was effective in iPCR reactions. A single product of 750 bp was obtained with a minor contaminant at about 250 bp. This iPCR product was cleaved by BamHI as expected and was cloned into the pCRII vector using the PCR T/A cloning kit (Invitrogen, NV Leek, Netherlands following the manufacturer's instructions). The EcoRI insert of the resulting plasmid was sequenced at the Centre of Molecular Recognition, Department of Biochemistry, University of Cambridge (FIG. 4A). By comparison with the L. japonicus PS sequence, the genomic iPCR product matched the cDNA's 3′ and 5′ ends and was assumed to contain authentic PS flanking regions. The annotated nucleotide sequence is shown in FIG. 4B.

[0048] While primer and cDNA sequences were straightforwardly identified within the iPCR product, analysis of the flanking regions was more difficult, since intron-exon borders can only be identified with some confidence. Predicion of splice sites according to Hebsgaard et al. (1996) at the NetPlantGene Server (Center for Biological Sequence Analysis, Technical University of Denmark, Lyngby, Denmark) suggested possible donor splice sites at positions 258 and 281, and possible acceptor splice sites at positions 179, 316, 338 and 536 in the sequence given in FIG. 4B. These sites were found in the low probability threshold mode of the program to include nearly all true sites. Intriguingly, none of these splice sites are situated within regions corresponding to cDNA.

[0049] There is one sequence feature of value regarding the question of the true translation start site within PS. This is a stop codon in the 5′ flanking region, 21 bases upstream from the putative initiation site, which is in frame with the PS ORF. If this stop codon forms part of the PS 5′-leader sequence as was implied in the splice site predictions, the ORF as encoded by the PS cDNA could safely be assumed to be complete. Specifically, this conclusion is conditional upon the absence of acceptor splice sites in between stop codon and cDNA start. The primary sequence information as such seems reliable firstly because a DNA-polymerase with proof reading activity was used in the PCR amplification and secondly because the chromatograms generated in two sequencing runs are both unambiguous.

Example 5

[0050] Cloning Pantothenate Synthetase from Lotus japonicus into an Expression Vector

[0051] An expression cassette was generated from the L. japonicus cDNA for PS using the PCR method of MacFerrin et al (1990) Lotus panC ORF was amplified from ca. 25 ng of plasmid pLC, using the primers LC5 and LC3. LC5 was designed to the start, ATG, codon of PS with an XbaI site highlighted in bold type and a ribsome binding site, underlined, included in the PCR primer dCGCGCTCTAGAA GGAGGAATTTAAAATGGCACCMTGGTGATATCTGAT. LC3 was designed to include the stop codon (TTA) of the ORF and an XhoI restriction site, in bold, in the PCR primer: dGCGCGCTCGAGTTACAAGTTGATTICTATGTT.

[0052] The PCR product was cloned into pBLUESCRIPT SK⁻ (Stratagene Ltd. Cambridge Innovation Centre, 140 Cambridge Science Park, Milton Road, Cambridge, CB44GF, UK) using the XbaI and XhoI restriction sites incorporated in the primers, and the resulting clone was referred to as pSKL. The expression cassette was designed to contain the L. japonicus PS ORF as demonstrated FIG. 5. The correct construct was confirmed by DNA sequence analysis (data not shown).

Example 6

[0053] Expression of Pantothenate Synthetases from Lotus japonicus, Oryza saliva, and Saccharomyces cerevisiae in Escherichia coli

[0054]L. japonicus PS was expressed in an E coli panC mutant AT1371 because wild-type E. coli strains have considerable PS activity which would make purification of the recombinant enzyme more difficult. E. coli AT1371 (panC transformed with the Lotus panC overexpressing plasmid pSKL was grown from single colonies overnight in 10 ml LB cultures containing 100 μg/ml ampicillin. Four 500 ml aliquots of 2YT medium (1.6% (w/v) bactopeptone, 1.0% (w/v) yeast extract and 0.5% (w/v) NaCl in water) in 2 litre flasks containing 60 μg/ml ampicillin and 20 μg/ml IPTG were each inoculated with 5 ml of overnight culture and incubated at 37° C. with shaking (190 RPM) for 10 hours before harvesting. E coli cells were recovered by centrifugation (10 min, 5000 RPM) and immediately resuspended in 20 ml of buffer A (50 mM Tris.HCl, 1 mM EDTA, 0.1 mM DTT, pH 8.0). Cells were lysed by sonication. Two equal aliquots of the cell suspension were each sonicated 6 times for 30 seconds on ice, with a 30 second pause between each burst. Cell debris was removed by centrifugation (30 min, 12000 RPM) and the crude extract was assayed for enzymatic activity.

[0055] Along with the Lotus PS expression clone pSKL, expression of PS activity was examined with all other available PS clones, that is the lacZ-PS fusion clones of Lotus and rice (pLC and pRC, respectively), yeast panC (pYC1) and E. coli panC (pCL). However, unlike pSKL clones, no attempt was made to optimise expression. Crude extracts from E coli AT1371 transformed with these pantothenate synthase clones or with vector alone were assayed for pantothenate synthase activity using either pantoate or pantoyl-lactone as substrate. Crude extract from wild type E. coli was also assayed, and the results are shown in the appended table (Table 1) which includes previously reported PS activities. In all cases examined enzyme activities were much higher with pantoate than with pantoyl-lactone. Given that purified E. coli PS had no activity toward pantoyl-lactone (Miyatake et al., 1979), the residual activities seen here with the latter substrate are likely due to a hydrolysing activity present in the cell extracts. An activity that catalyses hydrolysis of pantoyl-lactone was previously implied by Maas (1952a and 1952b). Failure to detect activity in samples derived from the Lotus or rice panC-lacZ fusion clones indicates lack of expression of enzymatically active PS. However, these clones were successfully used to complement a panC lesion in E. coli and therefore must express at least low levels of PS activity. Activities found in wild type E. coli or AT1371 transformed with vector alone are in accordance with previously reported values.

Example 7

[0056] Purification of Recombinant Lotus japonicus Pantothenate Synthetase Expressed in Escherichia coli

[0057] A crude extract of E. coli AT1371 transformed with the Lotus panC expression clone pSKL was prepared as described in Example 6. Starting from this crude extract, PS was essentially purified in two steps, ammonium sulphate fractionation and anion exchange chromatography To the cleared extract (28 ml), a saturated solution of (NH₄)₂SO₄ (12 ml) was added to reach a final concentration of 30% (NH₄)₂SO₄. The solution was kept on ice for 1 hour with stirring to allow protein aggregates to form. Insoluble protein was removed by centrifugation (12,000 RPM, 30 minutes) at 4° C. The supernatant was recovered (36 ml) and brought to 40%0 (NH₄)₂SO₄ saturation by addition of 6 ml of saturated (NH₄)₂SO₄ solution. The solution was incubated and centrifuged as before. Pelleted protein aggregates were dissolved in 5 ml of buffer A and dialysed against 2 litres of buffer A overnight at −4 C. The dialysed solution was centrifuged at 12,000 RPM for 30 minutes, and the supernatant was directly used in the anion exchange chromatography step.

[0058] The sample (5 ml) was loaded onto a Pharmacia FPLC MonoQ HR10/10 column previously equilibrated in buffer A. The column was washed with equilibration buffer until A₂₈₀ of the eluate was constant and below 0.1, and a constant flow rate of 2 ml/min was maintained throughout the run. Protein was eluted in a linear gradient (80 ml) of 0-250 mM KCl in buffer A, and 1 ml fractions were collected throughout the gradient and assayed for PS activity. FIG. 6 shows the PS activity (FIG. 6A) and protein (FIG. 6B) profiles of, this chromatographic step. The majority of PS activity eluted at ca. 100 mM KCl concentration. A second peak of PS activity eluted well separated from the first at just under 200 mM KCl along the gradient. This peak was broader than the first one and contained a much smaller but significant amount of activity. Since a homogenous overexpression product would principally be expected to elute in a single peak, separation of PS activity into two peaks was at first held to be an artifact. However, using a different column (MonoQ HR16/10) or changing gradient parameters including a solute change from KCl to ammonium acetate made no difference to the elution pattern. Physical differences in between the PS proteins in peaks one and two that could account for this behaviour may be due to differential folding or post-translational processing. The fractions with highest PS activities in either peak were pooled as indicated in FIG. 6A. Fractions 29 through 32 within the first peak gave sample PS-I (4 ml) which recovered 73% of PS activity loaded onto the column. Likewise, fractions 57 through 60 from the second peak were pooled to give PS-II (4 ml) containing 12% of the original PS activity. Samples PS-I and PS-II together contained 21.7 mg of PS.

[0059] Both, PS-I and PS-II were dialysed against 1 litre of buffer A overnight at 4° C. and centrifuged to precipitate insoluble protein. 500 μl aliquots of both PS-I and PS-II were loaded onto a Pharmacia Superose 6 column equilibrated in buffer A, maintaining a constant flow rate of 0.5 ml per minute and collecting 1 ml fractions. PS activity from both samples eluted in single peaks at an equal retention volume after injection, indicating a similar native molecular weight for PS-I and PS-II. This step offers no further purification of PS. In fact, specific activity was slightly decreased in both cases as can be seen from the purification summary in Table 2. However, SDS-PAGE (Laemmli, 1970; Sambrook et al., 1989) analysis of these samples revealed removal of some protein contaminants through gel filtration. Fractions 16 and 17 were pooled in each case to give samples PS-I/GF and PS-II/GF. Physical characterisation of recombinant PS is dealt with in the next section and was carried out on both PS-I and PS-II while kinetic analysis (Example 9) was restricted to PS-I.

Example 8

[0060] Characterisation of the Recombinant Lotus japonicus Pantothenate Synthetase

[0061] In order to confirm the identity of the overexpressed Lotus PS, N-terminal protein sequencing (Table 3) and amino acid analysis (Table 4) was carried out at the Protein and Nucleic acid Chemistry Facility “in the Department of Biochemistry, University of Cambridge on an applied Biosystems 477A Protein Sequencer for both PS-I and PS-II.

[0062] Alignment of N-terminal sequences obtained for PS-I and PS-II to the theoretical N-terminus of L. japonicus PS in Table 3 demonstrated that the purified recombinant protein is PS from L. japonicus. The overexpressed protein was apparently processed at the N-terminus, and the majority of both PS-I and PS-II lacked two N-terminal residues (methionine and alanine). However, some of they protein only lacked methionine giving rise to the secondary sequences observed. PS-I and PS-II differ somewhat with respect to the proportions of these differentially processed species. This can be seen from the relative yields at which primary and secondary sequences were obtained. The less abundant protein species with N-terminal alanine sequenced at an average yield comprising 70% (PS-I) or 40% (PS-II) of that seen for the primary sequence.

[0063] The theoretical molecular weight of recombinant L. japonicus PS is 34.2 kD, and this value is in reasonable agreement with the subunit weight obtained by SDS-PAGE analysis of the purified overexpression product (ca. 37 kD). The native molecular weight of PS-I or PS-II was estimated by gel filtration to be 72.8 kD implying the native protein is a homodimer.

[0064] More accurate determination of the Lotus PS subunit molecular weight was achieved by electrospray mass spectroscopy ESMS (carried out on an electrospray ionisation (positive ion mode) quadrapole mass spectrometer (BioQ; VG, Manchester, UK) using software supplied by the manufacturer). The transformed mass data revealed the presence of two protein species both in PS-I and PS-II which differ by 72.3 Da and 70.3 Da, respectively. This corresponds well to the theoretically expected mass difference in between presence or absence of an N-terminal alanine, that is 71.0 Da. Protein sequencing of recombinant PS had already shown that the N-terminal methionine was missing from the overexpression product while the following alanine residue was only partially removed. The main ESMS signal (100%) belongs to the lighter species and does therefore in all likelihood correspond to PS with N-terminal proline. Likewise, the secondary signals obtained at 75% (PS-I) or 40% (PS-II) relative intensity are due to PS with N-terminal alanine. As was concluded from the N-terminal sequencing data, the relative proportions of lighter and heavier PS species obtained here indicate PS-II was more efficiently processed than PS-I.

[0065] The L. japonicus PS ORF encodes a polypeptide of 308 residues with a predicted molecular weight of 34.2 kDa, and the processed recombinant protein (3-proline through 308-leucine) has a theoretical mass of 34,037.7 Da.

[0066] This is only in rough accordance with the weights obtained for PS-I (33,969.0±12.3 Da) and PS-II (33,967.0±10.2 Da), that is these proteins are lighter than expected by 68.7 Da and 70.7 Da, respectively. Given the accuracy of ESMS mass determinations, this discrepancy is presumably not due to a machine artifact. A possible explanation for the mass differences would be a mutation in the overexpression clone that might have been introduced through the PCR amplification of the L. japonicus panC expression cassette. However, the PCR step in question was carried out using a polymerase mix including a proof-reading activity, and, as mentioned earlier, no nucleotide sequence changes were found in between panC cDNA and expression cassette. Alternatively, the overexpressed PS may have been further processed at the C-terminus, for example.

Example 9

[0067] A High-Throughput Assay for Pantothenate Synthetase Activity

[0068] Three different assays have been reported previously for measuring PS activity (see above). The assays described by Maas (1950a and 1950b) and Miyatake et al (1979) are either microbiological or radiometric, while the number of auxilary enzymes and substrates required for the assay developed by Pfleiderer et al (1960) makes this assay cumbersome, expensive, and limited in its application to low throughput screening only. Hence, all three assays are unsuitable for the large scale high throughput biochemical screening of compounds necessary to discover new inhibitors of PS.

[0069] The applicants have developed in vitro assays which can be employed for high throughput biochemical screening for detecting inhibitors of this enzyme, to the use of these assays in the development of novel herbicides and in determining their mode of action, and to biological active inhibitors of pantothenate biosynthesis and herbicides obtained thereby. The assays are designed to measure the pyrophosphate liberated in the PS reaction either directly with a modified version of the calorimetric assay for the determination of inorganic pyrophosphate originally described by Chang et al. (1983); or after its conversion with inorganic pyrophosphatase to inorganic phosphate, which is then determined with modified versions of the calorimetric assays for the determination of inorganic phosphate originally described by Lanzetta et al. (1979) or Chifflet et al. (1988). The assays are carried out at room temperature, preferably on a microtiter scale.

[0070] 1. The preferred assay mixture to colorimetrically measure the pyrophosphate liberated in the PS reaction comprises 100 μmol Tris.HCl SpH 8.0), 10 μmol MgSO₄, 5 μmol ATP, 10 μmol β-alanine, 0.5 μmol pantoate and pantothenate synthetase in a total volume of 100 μl. After a suitable incubation period the PS reaction is terminated by the addition of 10 μl of a 0.8 M 2-mercaptoethanol in a 10% (w/v) solution of sodium dodecylsulfate followed by the addition of 50 μl of a 2.5% (w/v) solution of ammoniumheptamolybdate in 5 N sulfuric acid. After 20 minutes incubation at room temperature the intensity of the colour complex is determined by measuring the extinction at 620 nm. The amount of pyrophosphate liberated in the PS reaction is determined by reference to a standard curve generated from suitable amounts of pyrophosphate by using the difference of extinction at 620 nm between a complete PS assay mixture and a PS assay mixture lacking pantoate. One” unit of PS activity is defined as the amount of enzyme producing 1 mmole of pyrophosphate per minute, and specific activity is expressed as units per milligram of protein.

[0071] 2. The preferred assay mixture to measure the pyrophosphate liberated in the PS reaction after its conversion with inorganic pyrophosphatase to inorganic phosphate comp-rises 100 μmol Tris.HCl (pH 8.0), 10 μmol MgSO₄, 5 μmol ATP, 10 μmol O-alanine, 0.5 μmol pantoate, 1.0 unit yeast inorganic pyrophosphatase and pantothenate synthetase in a total volume of 100 μl. After a suitable incubation period the PS reaction is terminated either

[0072] a) by the addition of 100 μl of a reagent mixture comprising 62.3 □g malachite green hydrochloride, 1.9 mg ammoniumheptamolybdate and 0.5% (v/v) of a suitable detergent (for example Triton X-100, Tween-80 or Tergitol NPX) in 1.88 N hydrochloric acid. The resulting colour complex is stabilised by the addition after 1 minute of 50 μl of a 26% (w/v) solution of trisodium citrate dihydrate in water and after an additional 45 minutes incubation at room temperature the intensity of the colour complex is determined by measuring, the extinction at 620 nm. The amount of inorganic phosphate liberated in the PS reaction is determined by reference to a standard curve generated from suitable amounts of inorganic phosphate by using the difference of extinction at 620 nm between a complete PS assay mixture and a PS assay mixture lacking pantoate. Since there are 2 molecules of inorganic phosphate liberated for every molecule of pyrophosphate formed in the PS reaction, one unit of PS activity is defined as the amount of enzyme producing 2 nmoles of inorganic phosphate per minute, and specific activity is expressed as units per milligram of protein; or

[0073] b) by the addition of 100 μl of a reagent mixture comprising 3 mg, ascorbic acid, 0.5 mg ammoniumheptamolybdate and 1 mg sodium dodecylsulfate in 0.7 N hydrochloric acid. The resulting colour complex is stabilised by the addition after 7 minutes of 50 μl of a 6% (w/v) solution of trisodium citrate dihydrate in water and after an additional 20 minutes incubation at room temperature the intensity of the colour complex is determined by measuring the extinction at 620 nm. The amount of inorganic phosphate liberated in the PS reaction is determined by reference to, a standard curve generated from suitable amounts of inorganic phosphate by using the difference of extinction at 620 nm between, a complete PS assay mixture and a PS assay mixture lacking pantoate. Since there are 2 molecules of inorganic phosphate liberated for every molecule of pyrophosphate formed in the PS reaction, one unit of PS activity is defined as the amount of enzyme producing 2 nmoles of inorganic phosphate per minute, and specific activity is expressed as units per milligram of protein.

[0074] In order to determine the linear range of the assay used here, recombinant PS purified through the anion exchange chromatography step was assayed by method 2a, using final β-alanine and pantoate concentrations of 10 mM and 0.5 mM, respectively. When various amounts of PS were assayed, a proportional relationship of inorganic phosphate formed and enzyme amount was obtained in between 1 and 4 μg of protein (FIG. 7A). Furthermore, when a given amount of PS was assayed for different time periods, a proportional relationship of inorganic phosphate formed and incubation time is obtained in between 0 and 20 minutes of incubation (FIG. 7B).

Example 10

[0075] Biochemical Properties of Recombinant Lotus japonicus Pantothenate Synthetase

[0076] The recombinant L. japonicus enzyme investigated here was found to require pantoate, β-alanine, ATP and Mg²⁺ for activity. The pantoate analogues pantoyl-lactone and ketopantoate were not active as substrates in the place of pantoate. When present at 10-fold excess over pantoate, these analogues did not effect significant inhibition (Table 5).

[0077] With 100 nM Tris.HCl buffer optimal PS activity was achieved at pH 8.0. Activity decreases sharply towards more acidic pH's and is nil at pH 7.0, while there is only a slight decrease towards higher pH's with ca. 75% activity left at pH 9.0.

[0078] K_(m) and V_(max) constants for pantoate and β-alanine were determined by measuring the effect of substrate concentration on the reaction rate. Either pantoate or β-alanine were kept at a constant concentration of either 0.5 or 20 mM, and activity assays were carried out using variable concentrations of the other. Plotting the PS activity as a function of substrate concentration according to Lineweaver and Burk (1934) and Eadie (1942) and Hofstee (1959) revealed the kinetic constants as listed in Table 6.

[0079] Lotus PS suffers from substrate inhibition by pantoate, which becomes significant at pantoate concentrations of 400 μM or higher. The effect of pantoate concentration on K_(m) and V_(max) for β-alanine was as, expected for pure uncompetitive inhibition, that is both constants decreased with increasing pantoate concentration while their ratio remained constant. K_(m) over V_(max) for β-alanine derived from Lineweaver-Burk analysis equalled 0.106 and 0.104 for pantoate concentrations of 20 mM and 0.5 mM, respectively. When the rate equation for uncompetitive substrate inhibition was fitted to the PS activity data for pantoate, values of 42±2 μM and 5.33±0.34 mM were derived for K_(S) and K'_(S), respectively. V_(max) is 11.03±0.19 units in this fit which is equal to a k_(cat) value of 0.625±0.011 sec⁻¹. The K_(S) and k_(cat) values are very similar to K_(m) and k_(cat) as derived from linearised plots of activity data.

[0080] Using the rate equation for uncompetitive substrate inhibition and the values for K_(S) and K'_(S) obtained in the fit, an optimal pantoate concentration of 470±30 μM was calculated.

[0081] PS was also assayed in the presence of various compounds that might be expected to possess regulatory properties towards the enzyme. Among these compounds are the intermediates of pantothenate biosynthesis as well as coenzyme A. As coenzyme A plays a prominent role in fatty acid synthesis and degradation, various acyl forms of coenzyme A and free fatty acids were also included. PS was not assayed at optimal substrate concentrations, but pantoate and β-alanine were present at concentrations close to the respective K_(m) values (0.1 mM and 1 mM). Table 7 lists the compounds tried and their effect on PS activity which is expressed percentage of activity in an assay without additions.

REFERENCES

[0082] Bradford, M. M. (1976) Anal. Biochem. 72, 248-254.

[0083] Chang, G. G., Pan, F. Yeh, C., and Huang, T. M. (1983) Anal. Biochem. 130, 171.

[0084] Chifflet, S., Torriglia, A., Chiesa, R., and Tolosa, S. (1988) Anal. Biochem. 168, 1.

[0085] Cronan, J. E., Littel, K. J. and Jackowski, S. (1982) J. Bacterol.-149, 916-922.

[0086] Cronan, J. E. (1980) J. Bacteriol. 141, 1291-1297.

[0087] Dellaporta, S. L., Wood, J., and Hicks, J. B. (1983) Plant Mol. Biol. Rep. 1, 19-21.

[0088] Eadie, G. S. (1942) J. Biol. Chem. 146, 85.

[0089] Hebsgaard, S. M., Korning, P. G., Tolstrup, N., Engelbrecht, J., Rouze, P., and Brunak, S. (1996) Nucl. Acids Res. 24, 3439-3452.

[0090] Hofstee, B. H. J. (1959) Nature 184, 1296.

[0091] Lanzetta, P. A., Alvarez, L. J., Reinach, P. S. and Candia, O. A (1979) Anal. Biochem. 100, 95-97.

[0092] Laemmli, U. K (1970) Nature 227, 680-685.

[0093] Lineweaver, H., and Burk, D. (1934) J. Am. Chem. Soc. 56, 658.

[0094] Maas, W. K. (1952a) J. Biol. Chem. 198, 23-32.

[0095] Maas, W. K. (1952b) J. Bact. 63, 227-232.

[0096] MacFerrin, K D., Terranova, M. P., Schreiber, S. L., and Verdine, G. L. (1990) Proc. Natl. Acad. Sci. USA 87,1937-1941.

[0097] Miyatake, K., Nakano, Y., and Kitaoka, S. (1979) Methods Enzymol. 62, 215-219.

[0098] Ochman, H, Ajioka, J. W., Garza, D., and Harti, D. L. (1989) Inverse PCR in PCR Technology, pp. 105-112, Erlich, H. A. ed., Stockton Press, New York.

[0099] Pfleiderer, G., Kreiling, A., and Wieland, T. (1960) Biochem. Z. 333, 302-307.

[0100] Sambrook, J., Fritsch, E. F., and Maniatis, T. (1989) Molecular Cloning: A Laboratory Manual, 2nd Ed., Cold Spring Harbor Laboratory Press, Cold Spring Harbor, N.Y.

[0101] Senecoff, J. F. and Meagher, R. B. (1993). Plant Physiol. 102: 387-399 TABLE 1 Expression of pantothenate synthetases in E. coli AT1371 (panC) and wild type strains E. coli Specific Activity [U/mg] using strain Vector Pantoate OR Pantoyl-lactone Reference AT1371 pSKL 8.7 not detected (panC) Lotus PS AT1371 pLC not detected not detected (panC) Lotus PS-lacZ AT1371 pRC not detected not detected (panC) rice PS-lacZ AT1371 pYC1 88.0 3.1 this study (panC) yeast PS AT1371 pCL 957.4 6.0 (panC) E. coli PS AT1371 pBluescript not detected not detected (panC) K12 — 13.4 — (wild type) K12 — 8.1-8.7 — Cronan (wild et al. type) (1982) AT1371 — < 0.001 — (panC) (not detected) B — 4.1 — Miyatake (wild et al. type) (1979) W (wild — 1.3 — Pfleiderer type) et al. (1961)

[0102] TABLE 2 Summary of the purification procedure for recombinant Lotus japonicus pantothenate synthetase. PS was assayed using pantoate and β-alanine at final concentrations of 1 mM and 10 mM, respectively. Protein was assayed according to the method of Bradford (1976), using the Bio-Rad Protein reagent and microprotein assay in accordance with the manufacturer's instructions. Bovine serum albumine was used to calibrate the assay. Specific- total protein total Units Activity recovery Sample (mg) (nmoles/min) (U/mg) (%) purification Cleared 908.6 27410.2 30.2 (100) (1) extract (NH₄)₂SO₄ 209.7 33030.6 157.5 121  5.2 30-40% MonoQ - PS-I 17.8 24160.8 1357.3  88 44.9 MonoQ - PS-II 3.9 4070.7 1038.5  15 34.1 Superose6 - 2.16 2386.6 1104.9  79^((b)) 36.3 PS-I^((a)) Superose6 - 0.44 400.8 911.0  79^((b)) 29.9 PS-II^((a))

[0103] TABLE 3 N-terminal protein sequences of PS-I and PS-II proteins and predicted sequence for Lotus japonicus pantothenate synthetase Predicted sequence (a): M A P M V I S D K D E M R K W S R - 1°  sequence (b):           P M V I S D K D E M R K W S R 20° sequence (b):         A P M V I S D K D E M R K W S R

[0104] TABLE 4 Amino acid compositions obtained by amino acid analysis for PS-I and PS-II. integer fit of measured mole ratios to expected values Amino acid expected value PS-I PS-II Cys  5 5.64 not determined Asp 33 35.24 33.67 Thr  6 6.14 6.71 Ser 23 18.79 19.96 Glu 30 24.78 25.19 Gly 26 28.50 26.20 Ala 19 20.02 19.76 Val 33 30.70 32.76 Met  7 7.03 not determined Ile 20 20.37 19.84 Leu 22 24.56 23.78 Tyr  7 7.01 6.5 Phe 13 15.07 13.01 His  8 7.64 12.11 Lys 20 20.89 22.52 Arg 17 16.97 16.17 Pro 12 11.67 10.82 Trp  5 not determined not determined 306 residues

[0105] TABLE 5 Substrate specificity of the recombinant Lotus japonicus pantothenate synthetase. change from Pantoate β-alanine standard assay activity (units) yield (%) 0.1 mM 1 mM — 12.51 (100) 0.1 mM — — 0 0 — 1 mM — 0 0 — 1 mM pantoyl-lactone <0.1 <1 (1.0 mM) — 1 mM pantoyl-lactone 0.15 1 (10 mM) — 1 mM ketopantoate 0 0 (1.0 mM) — 1 mM ketopantoate 0 0 (10 mM) 0.1 mM 1 mM pantoyl-lactone 11.53 92 (1.0 mM) 0.1 mM 1 mM ketopantoate 12.18 97 (1.0 mM)

[0106] TABLE 6 Steady state kinetic constants for the recombinant Lotus pantothenate synthetase. Substrate K_(m) ^((a)) [μM] V_(max) ^((a)) [units] k_(cat) ^((b)) [sec⁻¹] Pantoate  45 (LB) 11.36 (LB) 0.63 (β-alanine at 20 mM  44 (EH) 10.98 (EH) const.) β-alanine 990 (LB)  9.52 (LB) 0.54 (pantoate at 0.5 mM 986 (EH)  9.51 (EH) const.)

[0107] TABLE 7 Activity of recombinant Lotus pantothenate synthetase in the presence of various potential effectors. Pantothenate synthetase activity obtained with individual compounds is expressed as a percentage of activity in an assay without effector. The assay was carried out using pantoate and β-alanine at concentrations of 0.1 mM and 1.0 mM, respectively. Concentration Final activity Compound [mM] [%] — — (100) a-KIVA 1 89 Ketopantoate 1 97 Pantoyl-lactone 1 92 Pantothenate 1 98 Pyrophosphate 1 78 CoenzymeA 1 109 0.2 106 0.1 100 Acetyl-coA 0.100 93 Malonyl-coA 0.100 92 Palmitoleoyl-coA 0.022 114 Oleoyl-coA 0.024 108 Palmitic acid 0.060 115 0.015 135 0.002 133 Palmitoleic acid 0.100 100 0.020 116

FIGURES

[0108] Referring to FIG. 1.1 there is shown a partial restriction map (A), subcloning (B) and nucleotide sequencing (C) of pLC, a Lotus japonicus cDNA for pantotheate synthetase. A: The L. japonicus pantotheate synthetase cDNA (pLC) was isolated by functional complementation of E. coli AT1371 (panC). B represents the sub-clones needed for the DNA sequencing strategy which is summarised in C.

[0109] Referring to FIG. 1.2 there is shown the nucleotide sequence of the Lotus japonicus cDNA for pantothenate synthetase and its predicted amino acid sequence. FIG. 1.2 shows the DNA sequence of the 1.33 kb EcoRI to XhoI insert of pLC (described in FIG. 1.1). The open reading frame codes for a polypeptide of 308 amino acids with a predicted molecular mass of 34.2 kDa and with 61% similarity to PS from E. coli. The indicated translation start site is putative and the stop codon (TAA) is is translated as “*”. This ORF on pLC is in frame with lacZ which accounts for expression of functional enzyme in E. coli and hence the observed complementation effect

[0110] Referring to FIG. 2.1 there is shown partial restriction map (A), subcloning (B), and nucleotide sequencing (C) of the rice pantothenate synthetase cDNA. The original cDNA for rice gene, pRC1, was subcloned in order to obtain its complete nucleotide sequence. The arrows indicate the position, direction, and length of individual sequencing runs. The open arrow indicates the EST sequence (GenBank accession no. D25017).

[0111] Referring to FIG. 2.2 there is shown the nucleotide sequence of the rice cDNA for pantothenate synthetase and its predicted amino acid sequence. The figure shows the DNA sequence of the 1.26 kb SalI to NotI insert of pRC1 (FIG. 2.1). The ORF encodes a polypeptide of 313 residues with a predicted molecular mass of 33.9 kD. The indicated translation start site is putative, and the stop codon is translated as “*”.

[0112] Referring to FIG. 2.3 there is depicted a method for generating the lacZ-pantothenate synthetase fusion clone for the expression of rice pantothenate synthetase in E. coli. The orientation of the cDNA in pRC1 was changed to yield pRC2 where the open reading frame is under transcriptional control of the lacZ promoter. The lacZ-PS fusion was generated by deleting four base pairs from pRC2, and the resulting plasmid, pRC, was sequenced to confirm the deletion (data not shown).

[0113] Referring to FIG. 3.1, the alignment of pantothenate synthetase protein sequences is shown. The PS protein sequences predicted from known (Lotus japonicus, Oryza saliva, Escherichia coli, Bacillus subtilis, Synechocystis sp.) or putative (Saccharomyces cerevisiae, Schizosaccharomyces pombe) genes were aligned using CLUSTAL W(1.5) within the GCG software package. Fully conserved residues are marked “*”, functionally conserved ones are marked “.”. lotus: Lotus japonicus, rice Oryza saliva, coli: Escherichia coli (GenBank P31663), subt: Bacillus subtilis (GenBank P52998), syne: Synechocystis sp. (GenBank U44896), yeast: Saccharomyces cerevisiae (GenBank P40459), pombe: Schizosaccharomyces pombe (GenBank Q09673).

[0114] Referring to FIG. 3.2, the subcloning of yeast pantothenate synthetase for expression in E. coli is depicted. A: The λ bacteriophage clone IPM4950 was obtained from the Sanger Centre, Hinxton Hall, Cambridge, UK, where the yeast PS sequence had been generated. B+C: Yeast panC was subcloned in two steps to yield plasmid clone pYC1 where the gene is placed under transcriptional control of the lac promoter. The position of the ORF is indicated by arrows. A T3-primed sequencing reaction using pYC1 as template confirmed the identity of the EcoRV-HindIII insert of the plasmid.

[0115] Referring to FIG. 3.3, there is shown the nucleotide sequence of the: Saccharomyces cerevisiae genomic DNA fragment for pantothenate synthetase and its predicted amino acid sequence. FIG. 3.3 shows the nucleotide sequence of the 1.5 kb EcoRV to HindIII genomic DNA fragment of S. cerevisiae that forms the insert of pYC1. The predicted amino acid sequence of yeast PS appears below the open reading frame. A Shine-Dalgarno-like sequence upstream of the translation initiation codon that may fortuitously serve as a RBS in E. coli is underlined. §—EcoRV; ¶—HindIII.

[0116] Referring to FIG. 4 there is shown the inverse PCR product of Lotus japonicus genomic regions flanking panC. A: Schematic representation of the iPCR product cloned into pCRII. The EcoRI.EcoRI insert was sequenced using T7 and M13 reverse primers. Both sequence runs were performed in duplicate and spanned ca. 600 bases each. B: Nucleotide sequence of the cloned iPCR product. The indicated matches with panC cDNA mean identical sequences. Positions corresponding to the first base (5′-¶) or the last base (3′-§) of the panC cDNA are marked. Within the 5′ flanking genomic sequence, there is a stop-codon in frame with the panC ORF.

[0117] Referring to FIG. 5, the expression cassette PCR of Lotus japonicus pantothenate synthetase is shown.

[0118] Referring to FIG. 6, there is shown the anion exchange chromatographs of recombinant Lotus japonicus pantothenate synthetase is shown. A sample of ammonium sulphate precipitated and dialysed PS was subjected to anion exchange chromatography on a MonoQ HR10/10 column as described in Example 7. A: PS activity profile. Fractions 29 through 32 were pooled to give sample PS-I, and fractions 57 through 60 were pooled to give sample PS-II. B: Protein elution profile followed by continous measurement of A₂₈₀ and potassium chloride gradient employed.

[0119] Referring to FIG. 7 the results of a high-throughput assay for recombinant Lotus japonicus pantothenate synthetase is depicted graphically. Graph A shows the effect of enzyme concentration on the reaction rate. Specific amounts of MonoQ purified PS-I were assayed as described in Example 9, method 2a. The activity-response is proportional in a range from 1 to 4 μg PS per assay. Graph B shows the time course of inorganic phosphate formation. 1.2 mg (), 2.4 mg (▪), and 3.0 mg (▴) of MonoQ purified PS-I were assayed as described in Example 9, method 2a. The activity-response is proportional in a range from 0 to 20 minutes of incubation.

1 21 1 1338 DNA Lotus japonicus 1 gaattcggca cgagctccaa tggcaccaat ggtgatatct gataaggacg agatgcggaa 60 atggtcaagg tccatgcgat cccaaggcaa gctcatcgcc ctcgttccca ccatgggctt 120 ccttcacgaa ggccaccttt ctctcgtcag agacgctcac aaccacgctg acctcgtcgc 180 cgtctcaatc tatgtcaacc ctggccagtt ttccccgacc gaggaccttt ccgcataccc 240 ttctgatttt caaggtgatc tccaaaaact catgtctgtt cctggtggtg ttgatgttgt 300 tttccacccc cacaatttgt atgattacgg tggtgatggc ggtgatgctg tggcggagtg 360 tggtggtgat ggggtggtgt cttgtgttga taggaggagt ggttttgggc atgaaacttg 420 ggttagagct gagaagctgg agaaacccct ttgtgggaag agtaggcctg ttttctttag 480 aggggttgcc accattgtta ccaagttgtt taatattgtg gagcctgatg ttgctgtgtt 540 tgggaagaag gactatcagc aatggaaaat tattcagaga atggttcgag atcttgattt 600 ttccataaaa gtgataggtt ctgaagtaat acgtgagaaa gatggcctag caatgagttc 660 ccgtaatgtg tacctatcac ctgaagagag ggaaaaggca gtatctataa ataaatcatt 720 gtttagagct aaatcggcag cagaagatgg acagatacat tgtgagaaat tgataaactt 780 ggtcgtgcaa agtatcaccg aagctggtgg aaggattgat tatgctgaga ttgttgatca 840 aaataatttg gagaaagtgg aatggatcaa gggtcctgtt gtcttctgtg tttctgcatg 900 gtttgggaaa gccaggctta tagacaacat agaaatcaac ttgtaaatgg aagtaagatt 960 gatctaacct tgtgaataat ctcagacatg gaccatatga ttagtagttc tggcatttca 1020 tggggtatag acttcattct acaagccatg atatgactac ttgtagatgt attttactac 1080 ctcatgaaat tctaggagct gcttctattt gttggtgatg gtataatatt ttgcagagcc 1140 accactccag aggaaaacaa aattagagaa atcttgctta tgtatcaaag tgccccaggt 1200 ttactcatta atctagataa atctgagctt tctttaggct gatgtacgcc tagagataga 1260 caaacataat tctggtgctg gataaaatta acgcattgga ttcccatttg aaataaaaaa 1320 aaaaaaaaaa aactcgag 1338 2 1264 DNA Oryza sativa 2 gtcgacccac gcgtccggtt tctccctgtc cacttctgtc cgattcctcc tcacctctta 60 tcgattggac gaccatggcg gcgccgcgcg agccggaggt gatccgcgac aaggcggcga 120 tgcgcgcatg gtcgcgccgc cgtcgcgccg agggcaagac cgtcgcggtc gtacccacca 180 tgggctacct ccaccaaggc cacctctccc tcatctccgc cgccgccgcc gccgcctccg 240 ctgatcccgt cgccatcgtc gtcaccatct acgtcaaccc cagccagttc gcgccctcag 300 aggacctcgc cacctaccct tccgacttcg ccggtgacct ccgcaagctc gcctccaccg 360 gcgtcgtgga tgccgtcttc aacccccctg acctctacgt ccgtggcgcc ggtcgccgcg 420 gggccggctc cggaggcgcg atctcctgcc tggaggaggc ggccggggat gggcacgaga 480 cgtgggttcg ggtggagcga ttggagaagg gattgtgcgg ggccagccgt cccgtgttct 540 tccgaggcgt ggccaccata gtctccaagc tgtttaacat catcgagccg gatgttcctg 600 tgttcgggaa gaaggattat cagcagtggc gcgtcatctt gccgtattgg tcgggacttg 660 attttggcat agagataatg ggatcaagaa attgtgcgag aactgatggt cttgccatga 720 actcccggaa tgtgcaccta tcacgcgagg aagggaaaaa ggcattatcc atcagtagat 780 cactggttga tgctagaact ggcgccttga agggaaacac tgattccaaa caaatcaaaa 840 acaaaatagt acagacacta actgaaactg gcggtcaggt tgactatgtt gagatcgtgg 900 agcaagaaag tttggtccct gtagaacaga tcgacggccc tgtggtcatt tgcgttgcgg 960 cgtggtttgg aaaggtcagg ctgatcgata atatcgaaat cgatacacga tcctgaggtt 1020 ttggggggat tcacttgctg tctgctgtga ccttggcatt gcgtttgaaa taccttttgt 1080 ttcgcgtgat gattcgcgtc atgttgtacg ctgtaacaat cacagagaga aaatatgcag 1140 gagtacactg actgaaggca aatttataag tacaaactgt agaggcctga tgctgtaaca 1200 ggggaaatca tgcttgttga ttacagattc cgctgaaaaa aaaaaaaaaa aaaagggcgg 1260 ccgc 1264 3 1500 DNA Saccharomyces cerevisiae 3 gatatccggg taaatgttac tttaacgagt ttttttcttt tgtcatattt tccaacaaga 60 gattaatgaa catttctcga tgtagcgtac atatttatgt gtacaagaag tggtgtgtgt 120 tgatactgca ctgttttata caagttttta tactgcatat ccatatagaa ttgatgaaaa 180 tcttccatac tgtcgaagaa gttgttcaat ggagaacaca ggagctgagg gaaactagat 240 ttagagaaac tattgggttc gttcccacaa tgggttgcct gcattcgggt cacgctagtt 300 tgatctcgca gtctgtgaag gaaaacacct atactgtggt cagtatattt gtaaatccct 360 cccagtttgc gccaacggaa gatctagata actatcctcg aactttgcca gacgacatca 420 aattgcttga gtcgttgaag gtggatgttc tatttgctcc taatgcacac gtgatgtatc 480 cacagggaat tccgctcgac atagaagagc agaaaggccc ttttgttagt gttcttggat 540 tgagtgaaaa attagagggg aagacgagac ctaacttctt taggggcgtg gcaactgtcg 600 tgactaaact attcaatatc gttatggcgg atgtggctta ttttgggcag aaggacattc 660 aacagttcat tgttttacag tgtatggtgg acgaactgtt tgttaataca aggctacaaa 720 tgatgcctat tgtaagaaac aataatggac tggctctgag tagtagaaac aaatatcttt 780 gtccagagtc tttaaagatc tctgaaaacc tttaccgcgg gctgaaagct gcggaaaatg 840 ctattaggag actagcacca gggggacgtc tctccagatc agaaatcatc gatactgtga 900 ctcaaatatg ggcaccctac gttgattccc acgatttcaa aatcgactat gtttccttag 960 cagattttaa gactcttgat gaactctccg atgttgaaaa caccagcgaa cagcagccaa 1020 tagtcattag ttgtgctgta tacgtgactg accgcgaaaa acccgatacg gtcgtcagac 1080 taatagataa catcgttatt taaactaggt gattgggcct tcccgtgtct gtgttgcagt 1140 atataccact cttatacagt atgcacgata ttcttttaaa ccaacaacgg gatgatagat 1200 ttcacgcttg atgacttttt ttttagacgg ctgaagggac gacatcccca tcgctcaaaa 1260 cacaaatatg gaaaggacaa atcgtctttc acagtttgca tagtaaaagc aaagtttata 1320 ctacttcagc aaagttgaag ttgtttggca cttgtttcgt gctttctcaa atatcttaga 1380 tcaccgtctg tctagagcat atatctattg tttgacgcac cccttttaca aaaaaaaaaa 1440 aaagaaacag atctattaag taataaaaaa gttatttagg aaataaggtg cagtaagctt 1500 4 308 PRT Lotus japonicus 4 Met Ala Pro Met Val Ile Ser Asp Lys Asp Glu Met Arg Lys Trp Ser 1 5 10 15 Arg Ser Met Arg Ser Gln Gly Lys Leu Ile Ala Leu Val Pro Thr Met 20 25 30 Gly Phe Leu His Glu Gly His Leu Ser Leu Val Arg Asp Ala His Asn 35 40 45 His Ala Asp Leu Val Ala Val Ser Ile Tyr Val Asn Pro Gly Gln Phe 50 55 60 Ser Pro Thr Glu Asp Leu Ser Ala Tyr Pro Ser Asp Phe Gln Gly Asp 65 70 75 80 Leu Gln Lys Leu Met Ser Val Pro Gly Gly Val Asp Val Val Phe His 85 90 95 Pro His Asn Leu Tyr Asp Tyr Gly Gly Asp Gly Gly Asp Ala Val Ala 100 105 110 Glu Cys Gly Gly Asp Gly Val Val Ser Cys Val Asp Arg Arg Ser Gly 115 120 125 Phe Gly His Glu Thr Trp Val Arg Ala Glu Lys Leu Glu Lys Pro Leu 130 135 140 Cys Gly Lys Ser Arg Pro Val Phe Phe Arg Gly Val Ala Thr Ile Val 145 150 155 160 Thr Lys Leu Phe Asn Ile Val Glu Pro Asp Val Ala Val Phe Gly Lys 165 170 175 Lys Asp Tyr Gln Gln Trp Lys Ile Ile Gln Arg Met Val Arg Asp Leu 180 185 190 Asp Phe Ser Ile Lys Val Ile Gly Ser Glu Val Ile Arg Glu Lys Asp 195 200 205 Gly Leu Ala Met Ser Ser Arg Asn Val Tyr Leu Ser Pro Glu Glu Arg 210 215 220 Glu Lys Ala Val Ser Ile Asn Lys Ser Leu Phe Arg Ala Lys Ser Ala 225 230 235 240 Ala Glu Asp Gly Gln Ile His Cys Glu Lys Leu Ile Asn Leu Val Val 245 250 255 Gln Ser Ile Thr Glu Ala Gly Gly Arg Ile Asp Tyr Ala Glu Ile Val 260 265 270 Asp Gln Asn Asn Leu Glu Lys Val Glu Trp Ile Lys Gly Pro Val Val 275 280 285 Phe Cys Val Ser Ala Trp Phe Gly Lys Ala Arg Leu Ile Asp Asn Ile 290 295 300 Glu Ile Asn Leu 305 5 313 PRT Oryza sativa 5 Met Ala Ala Pro Arg Glu Pro Glu Val Ile Arg Asp Lys Ala Ala Met 1 5 10 15 Arg Ala Trp Ser Arg Arg Arg Arg Ala Glu Gly Lys Thr Val Ala Val 20 25 30 Val Pro Thr Met Gly Tyr Leu His Gln Gly His Leu Ser Leu Ile Ser 35 40 45 Ala Ala Ala Ala Ala Ala Ser Ala Asp Pro Val Ala Ile Val Val Thr 50 55 60 Ile Tyr Val Asn Pro Ser Gln Phe Ala Pro Ser Glu Asp Leu Ala Thr 65 70 75 80 Tyr Pro Ser Asp Phe Ala Gly Asp Leu Arg Lys Leu Ala Ser Thr Gly 85 90 95 Val Val Asp Ala Val Phe Asn Pro Pro Asp Leu Tyr Val Arg Gly Ala 100 105 110 Gly Arg Arg Gly Ala Gly Ser Gly Gly Ala Ile Ser Cys Leu Glu Glu 115 120 125 Ala Ala Gly Asp Gly His Glu Thr Trp Val Arg Val Glu Arg Leu Glu 130 135 140 Lys Gly Leu Cys Gly Ala Ser Arg Pro Val Phe Phe Arg Gly Val Ala 145 150 155 160 Thr Ile Val Ser Lys Leu Phe Asn Ile Ile Glu Pro Asp Val Pro Val 165 170 175 Phe Gly Lys Lys Asp Tyr Gln Gln Trp Arg Val Ile Leu Pro Tyr Trp 180 185 190 Ser Gly Leu Asp Phe Gly Ile Glu Ile Met Gly Ser Arg Asn Cys Ala 195 200 205 Arg Thr Asp Gly Leu Ala Met Asn Ser Arg Asn Val His Leu Ser Arg 210 215 220 Glu Glu Gly Lys Lys Ala Leu Ser Ile Ser Arg Ser Leu Val Asp Ala 225 230 235 240 Arg Thr Gly Ala Leu Lys Gly Asn Thr Asp Ser Lys Gln Ile Lys Asn 245 250 255 Lys Ile Val Gln Thr Leu Thr Glu Thr Gly Gly Gln Val Asp Tyr Val 260 265 270 Glu Ile Val Glu Gln Glu Ser Leu Val Pro Val Glu Gln Ile Asp Gly 275 280 285 Pro Val Val Ile Cys Val Ala Ala Trp Phe Gly Lys Val Arg Leu Ile 290 295 300 Asp Asn Ile Glu Ile Asp Thr Arg Ser 305 310 6 283 PRT Escherichia coli 6 Val Leu Ile Ile Glu Thr Leu Pro Leu Leu Arg Gln Gln Ile Arg Arg 1 5 10 15 Leu Arg Met Glu Gly Lys Arg Val Ala Leu Val Pro Thr Met Gly Asn 20 25 30 Leu His Asp Gly His Met Lys Leu Val Asp Glu Ala Lys Ala Arg Ala 35 40 45 Asp Val Val Val Val Ser Ile Phe Val Asn Pro Met Gln Phe Asp Arg 50 55 60 Pro Glu Asp Leu Ala Arg Tyr Pro Arg Thr Leu Gln Glu Asp Cys Glu 65 70 75 80 Lys Leu Asn Lys Arg Lys Val Asp Leu Val Phe Ala Pro Ser Val Lys 85 90 95 Glu Ile Tyr Pro Asn Gly Thr Glu Thr His Thr Tyr Val Asp Val Pro 100 105 110 Gly Leu Ser Thr Met Leu Glu Gly Ala Ser Arg Pro Gly His Phe Arg 115 120 125 Gly Val Ser Thr Ile Val Ser Lys Leu Phe Asn Leu Val Gln Pro Asp 130 135 140 Ile Ala Cys Phe Gly Glu Lys Asp Phe Gln Gln Leu Ala Leu Ile Arg 145 150 155 160 Lys Met Val Ala Asp Met Gly Phe Asp Ile Glu Ile Val Gly Val Pro 165 170 175 Ile Met Arg Ala Lys Asp Gly Leu Ala Leu Ser Ser Arg Asn Gly Tyr 180 185 190 Leu Thr Ala Glu Gln Arg Lys Ile Ala Pro Gly Leu Tyr Lys Val Leu 195 200 205 Ser Ser Ile Ala Asp Lys Leu Gln Ala Gly Glu Arg Asp Leu Asp Glu 210 215 220 Ile Ile Thr Ile Ala Gly Gln Glu Leu Asn Glu Lys Gly Phe Arg Ala 225 230 235 240 Asp Asp Ile Gln Ile Arg Asp Ala Asp Thr Leu Leu Glu Val Ser Glu 245 250 255 Thr Ser Lys Arg Ala Val Ile Leu Val Ala Ala Trp Leu Gly Asp Ala 260 265 270 Arg Leu Ile Asp Asn Lys Met Val Glu Leu Ala 275 280 7 286 PRT Bacillus subtilis 7 Met Arg Gln Ile Thr Asp Ile Ser Gln Leu Lys Glu Ala Ile Lys Gln 1 5 10 15 Tyr His Ser Glu Gly Lys Ser Ile Gly Phe Val Pro Thr Met Gly Phe 20 25 30 Leu His Glu Gly His Leu Thr Leu Ala Asp Lys Ala Arg Gln Glu Asn 35 40 45 Asp Ala Val Ile Met Ser Ile Phe Val Asn Pro Ala Gln Phe Gly Pro 50 55 60 Asn Glu Asp Phe Glu Ala Tyr Pro Arg Asp Ile Glu Arg Asp Ala Ala 65 70 75 80 Leu Ala Glu Asn Ala Gly Val Asp Ile Leu Phe Thr Pro Asp Ala His 85 90 95 Asp Met Tyr Pro Gly Glu Lys Asn Val Thr Ile His Val Glu Arg Arg 100 105 110 Thr Asp Val Leu Cys Gly Arg Ser Arg Glu Gly His Phe Asp Gly Val 115 120 125 Ala Ile Val Leu Thr Lys Leu Phe Asn Leu Val Lys Pro Thr Arg Ala 130 135 140 Tyr Phe Gly Leu Lys Asp Ala Gln Gln Val Ala Val Val Asp Gly Leu 145 150 155 160 Ile Ser Asp Phe Phe Met Asp Ile Glu Leu Val Pro Val Asp Thr Val 165 170 175 Arg Glu Glu Asp Gly Leu Ala Lys Ser Ser Arg Asn Val Tyr Leu Thr 180 185 190 Ala Glu Glu Arg Lys Glu Ala Pro Lys Leu Tyr Arg Ala Leu Gln Thr 195 200 205 Ser Ala Glu Leu Val Gln Ala Gly Glu Arg Asp Pro Glu Ala Val Ile 210 215 220 Lys Ala Ala Lys Asp Ile Ile Glu Thr Thr Ser Gly Thr Ile Asp Tyr 225 230 235 240 Val Glu Leu Tyr Ser Tyr Pro Glu Leu Glu Pro Val Asn Glu Ile Ala 245 250 255 Gly Lys Met Ile Leu Ala Val Ala Val Ala Phe Ser Lys Ala Arg Leu 260 265 270 Ile Asp Asn Ile Ile Ile Asp Ile Arg Glu Met Glu Arg Ile 275 280 285 8 275 PRT Synechocystis sp 8 Val Gln Val Phe Arg Thr Ile Ala Gly Leu Gln Thr Tyr Leu Arg Gln 1 5 10 15 Ala Gly Arg Gly Lys Thr Val Gly Leu Val Pro Thr Met Gly Ser Leu 20 25 30 His Ala Gly His Gly Ser Leu Leu Lys Arg Ala Val Ala Glu Met Asp 35 40 45 Leu Val Val Leu Ser Ile Phe Val Asn Pro Leu Gln Phe Gly Pro Gly 50 55 60 Glu Asp Leu Glu Lys Tyr Pro Arg Asp Phe Asp Gly Asp Arg Gln Trp 65 70 75 80 Ala Glu Ser Leu Gly Val Ala Val Ile Phe Ala Pro Thr Val Thr Asp 85 90 95 Leu Gly Ile Asp Ala Lys Gly Asp Gln Thr Thr Val Leu Pro Pro Pro 100 105 110 Ala Met Thr Glu Val Leu Cys Gly Ala His Arg Pro Gly His Phe Gln 115 120 125 Gly Val Ala Thr Ile Val Thr Lys Leu Phe Thr Ile Val Cys Pro Asp 130 135 140 Val Ala Tyr Phe Gly Ala Lys Asp Ala Gln Gln Leu Ala Ile Ile Arg 145 150 155 160 Arg Leu Val Gln Asp Leu Asn Leu Thr Val Thr Ile Arg Ser Cys Ala 165 170 175 Thr Val Arg Glu Glu Ser Gly Leu Ala Met Ser Ser Arg Asn Gln Tyr 180 185 190 Leu Ser Pro Ile Glu Lys Glu Gln Ala Thr Val Leu Tyr Arg Ser Leu 195 200 205 Gln Ala Ala Pro Thr Ala Ile Ser Ser Arg Arg Ser Pro Ser Phe Cys 210 215 220 Phe Val Asp Arg His Pro Gly Arg Phe Gly Arg Gly Thr Val Leu Ser 225 230 235 240 Arg Cys Asn Ile Cys Asn Trp Trp Lys Leu Thr Pro Cys Gln Pro Ile 245 250 255 Thr Trp Asn Ile Thr Gly Pro Lys Ser Cys Phe Asn Gly Asp Arg Arg 260 265 270 Leu Cys Gly 275 9 345 PRT Saccharomyces cerevisiae 9 Met Asn Ile Ser Arg Cys Ser Val His Ile Tyr Val Tyr Lys Lys Trp 1 5 10 15 Cys Val Leu Ile Leu His Cys Phe Ile Gln Val Phe Ile Leu His Ile 20 25 30 His Ile Glu Leu Met Lys Ile Phe His Thr Val Glu Glu Val Val Gln 35 40 45 Trp Arg Thr Gln Glu Leu Arg Glu Thr Arg Phe Arg Glu Thr Ile Gly 50 55 60 Phe Val Pro Thr Met Gly Cys Leu His Ser Gly His Ala Ser Leu Ile 65 70 75 80 Ser Gln Ser Val Lys Glu Asn Thr Tyr Thr Val Val Ser Ile Phe Val 85 90 95 Asn Pro Ser Gln Phe Ala Pro Thr Glu Asp Leu Asp Asn Tyr Pro Arg 100 105 110 Thr Leu Pro Asp Asp Ile Lys Leu Leu Glu Ser Leu Lys Val Asp Val 115 120 125 Leu Phe Ala Pro Asn Ala His Val Met Tyr Pro Gln Gly Ile Pro Leu 130 135 140 Asp Ile Glu Glu Gln Lys Gly Pro Phe Val Ser Val Leu Gly Leu Ser 145 150 155 160 Glu Lys Leu Glu Gly Lys Thr Arg Pro Asn Phe Phe Arg Gly Val Ala 165 170 175 Thr Val Val Thr Lys Leu Phe Asn Ile Val Met Ala Asp Val Ala Tyr 180 185 190 Phe Gly Gln Lys Asp Ile Gln Gln Phe Ile Val Leu Gln Cys Met Val 195 200 205 Asp Glu Leu Phe Val Asn Thr Arg Leu Gln Met Met Pro Ile Val Arg 210 215 220 Asn Asn Asn Gly Leu Ala Leu Ser Ser Arg Asn Lys Tyr Leu Cys Pro 225 230 235 240 Glu Ser Leu Lys Ile Ser Glu Asn Leu Tyr Arg Gly Leu Lys Ala Ala 245 250 255 Glu Asn Ala Ile Arg Arg Leu Ala Pro Gly Gly Arg Leu Ser Arg Ser 260 265 270 Glu Ile Ile Asp Thr Val Thr Gln Ile Trp Ala Pro Tyr Val Asp Ser 275 280 285 His Asp Phe Lys Ile Asp Tyr Val Ser Leu Ala Asp Phe Lys Thr Leu 290 295 300 Asp Glu Leu Ser Asp Val Glu Asn Thr Ser Glu Gln Gln Pro Ile Val 305 310 315 320 Ile Ser Cys Ala Val Tyr Val Thr Asp Arg Glu Lys Pro Asp Thr Val 325 330 335 Val Arg Leu Ile Asp Asn Ile Val Ile 340 345 10 283 PRT Schizosaccharomyces pombe 10 Met Gln Val Leu Lys Glu Lys Leu Leu Ile His Gln Gln Val Asp Asn 1 5 10 15 Trp Arg Lys Asp Gly Asn Arg Ile Ala Phe Val Pro Thr Met Gly Asn 20 25 30 Leu His Glu Gly His Phe Ser Leu Val Arg Glu Ala Lys Arg His Ala 35 40 45 Glu Lys Val Val Val Ser Ile Phe Val Asn Pro Met Gln Phe Asn Asn 50 55 60 Pro Gln Asp Leu Leu Leu Tyr Pro Arg Thr Met Asp Gln Asp Cys Ser 65 70 75 80 Gln Leu Gln Asn Leu Gly Val Asp Leu Val Tyr Ala Pro Thr Val Glu 85 90 95 Glu Leu Tyr Pro Glu Gly Ser Gln Asp Ile Thr Phe Val Asp Val Pro 100 105 110 Lys Leu Ser Thr Met Leu Glu Gly Ala Ser Arg Pro Gly His Phe Arg 115 120 125 Gly Val Thr Thr Val Val Ser Lys Leu Phe His Ile Val Asn Pro Asp 130 135 140 Val Ala Cys Phe Gly Glu Lys Asp Phe Gln Gln Val Ala Ile Ile Lys 145 150 155 160 Lys Met Val Arg Asp Leu Asn Phe Phe Ile Glu Ile Ile Gln Val Pro 165 170 175 Ile Val Arg Ala Asp Asp Gly Leu Ala Leu Ser Ser Arg Asn Gly Tyr 180 185 190 Leu Thr Ser Glu Glu Arg Lys Ile Ala Pro Asn Leu Tyr Lys Ile Leu 195 200 205 Lys Lys Leu Ala Gln Glu Leu Ser Asn Gly Asn Gly Asp Leu Glu Lys 210 215 220 Leu Ile Ala Glu Thr Asn Thr Glu Leu Ser Arg Cys Arg Phe Ile Pro 225 230 235 240 Asp Gln Leu Glu Ile Cys Asp Ser Thr Thr Leu Glu Pro Phe Thr Ala 245 250 255 Gly Thr Lys Asn Val Val Ile Leu Ala Ala Ala Trp Leu Gly Lys Ala 260 265 270 Arg Leu Ile Asp Asn Ile Gln Thr Thr Ile Asn 275 280 11 788 DNA Lotus japonicus 11 gaattcggct tcatcaagct tatgtatcaa agtgccccag gtttactcat taatctagat 60 aaatctgagc tttctttagg ctgatgtacg cctagagata gacaaacata attctggtgc 120 tggataaaat taacgcattg gattcccatt tgaaatatct tggtctccct attttatagg 180 aggatccaac ggcagagaac ctaggttctc atgacccctc ttgagggcca tcctagcttc 240 gggatctcat ataaaaggtc ccttacaaca aggggccaat gtaacttctc ttagctcaat 300 tactttgata acttagactt ttcatcctgc tgaaccagaa ttgacttagg catcaaagtg 360 gtttgcacga ccccctcccg ggcttacctg tacgttgcag actacctctc tccagtcgtt 420 cgctcgagct ccaacctccc tcacccccgt tccccttccc tcctacccct tcgtgggtag 480 tcttggtcga atcttcccgg atcaatatca tatatgatat catcatcatt tcaatagaat 540 gaagcgccac ctatctattt gcttcatcaa aagccttctt ttgcaagagt tcccatttgt 600 tcttatcacc ttcacgttca actagcttta cactttttcg acattcccaa taacaacacc 660 agaaccctcc tccaatggca ccaatggtga tatctgataa ggacgagatg cggaaatggt 720 caaggtccat gcgatcccaa ggcaagctca tcgccctcgt tcccaccatg gatcccgaag 780 ccgaattc 788 12 33 PRT Lotus Japonicus 12 Met Ala Pro Met Val Val Ile Ser Asp Lys Asp Glu Met Arg Lys Trp 1 5 10 15 Ser Arg Ser Met Arg Ser Gln Gly Lys Leu Ile Ala Leu Val Pro Thr 20 25 30 Met 13 24 DNA Lotus japonicus 13 atggcaccaa tggtgatatc tgat 24 14 21 DNA Lotus japonicus 14 ttgtatcttt agttgaacat t 21 15 31 DNA Lotus japonicus 15 cgggatccat ggtgggaacg agggcgatga g 31 16 30 DNA Lotus japonicus 16 catcaagctt atgtatcaaa gtgccccagg 30 17 49 DNA Lotus japonicus 17 cgcgctctag aaggaggaat ttaaaatggc accaatggtg atatctgat 49 18 32 DNA Lotus japonicus 18 gcgcgctcga gttacaagtt gatttctatg tt 32 19 17 PRT Lotus japonicus 19 Met Ala Pro Met Val Ile Ser Asp Lys Asp Glu Met Arg Lys Trp Ser 1 5 10 15 Arg 20 15 PRT Lotus japonicus 20 Pro Met Val Ile Ser Asp Lys Asp Glu Met Arg Lys Trp Ser Arg 1 5 10 15 21 16 PRT Lotus japonicus 21 Ala Pro Met Val Ile Ser Asp Lys Asp Glu Met Arg Lys Trp Ser Arg 1 5 10 15 

1. An isolated DNA molecule encoding a protein from a plant, which protein has pantothenate synthetase activity.
 2. An isolated DNA molecule according to claim 1, wherein the plant is Lotus japonicus.
 3. An isolated DNA molecule according to claim 2, wherein the DNA molecule encodes a protein comprising the amino acid sequence set forth in FIG. 1.2.
 4. An isolated DNA molecule according to claim 3, wherein the DNA molecule comprises the nucleotide sequence set forth in FIG. 1.2.
 5. An isolated DNA molecule according to claim 1, wherein the plant is Oryza sativa.
 6. An isolated DNA molecule according to claim 5, wherein the DNA molecule encodes a protein comprising the amino acid sequence set forth in FIG. 2.2.
 7. An isolated DNA molecule according to claim 6, wherein the DNA molecule comprises the nucleotide sequence set forth in FIG. 2.2.
 8. A non-naturally occuring chimeric gene comprising a promoter operably linked to a DNA molecule encoding a protein from a plant having pantothenate synthetase activity.
 9. A non-naturally occuring chimeric gene according to claim 8 wherein the protein comprises an amino acid sequence selected from the group set forth in FIG. 1.2 and FIG. 2.2.
 10. A recombinant vector comprising the chimeric gene of any of claims 8 to 9 wherein the vector is capable of being stably transformed into a host cell.
 11. A host cell stably transformed with the vector of claim 10 wherein the host cell is capable of expressing the DNA molecule.
 12. A host cell according to claim 11 selected from the group consisting of a bacterial cell, a yeast cell and an insect cell.
 13. A method of producing a protein having pantothenate synthetase activity in a host organism comprising, a) inserting a DNA sequence encoding a protein having antothenate synthetase activity into an expression casette designed for the chosen host; b) inserting the resultant molecule, containing the individual lements linked in proper reading frame, into a vector capable of being transformed into the host cell; c) growing the thus transformed host cell in a suitable culture medium; and d) isolating the protein product either from the transformed cell or the culture medium or both and purifying it.
 14. A method for assaying a protein having pantothenate synthetase activity comprising, a) incubating the protein in a suitable reaction mixture in which the protein is capable of catalyzing the conversion of pantoate, β-alanine and ATP to pantothenate, AMP and pyrophosphate; and b) determining the amount of pyrophosphate generated by the catalytic activity of pantothenate synthetase by a calorimetric technique.
 15. A method for assaying a protein having pantothenate synthetase activity comprising, incubating the protein in a suitable reaction mixture in which the protein is capable of catalyzing the conversion of pantoate, a) β-alanine and ATP to pantothenate, AMP and pyrophosphate; and b) converting the pyrophosphate formed by the catalytic activity of pantothenate synthetase into inorganic phosphate by the catalytic activity of an inorganic pyrophosphatase; and c) determining the amount of inorganic phosphate generated by the catalytic activity of the inorganic pyrophosphatase by a colorimetric technique.
 16. A method according to claim 15 wherein the inorganic pyrophosphatase is yeast pyrophosphatase.
 17. A method for assaying a chemical for the ability to inhibit the activity of a pantothenate synthetase enzyme from a plant comprising, a) incubating the pantothenate synthetase enzyme in a first reaction mixture under conditions specified in claim 14 or claim 15; b) combining the chemical and the pantothenate synthetase enzyme in a second reaction mixture under the same conditions as in the first reaction mixture; and c) measuring the amount of either pyrophosphate or inorganic phosphate in the first and second reaction mixtures; wherein the chemical is capable of inhibiting the activity of the pantothenate synthetase enzyme if the amount of either pyrophosphate formed or inorganic phosphate formed in the second reaction mixture is significantly less than the amount of either pyrophosphate formed or inorganic phosphate formed in the first reaction mixture.
 18. The use as herbicides of compounds which inhibit pantothenate synthetase.
 19. Herbicidal composition, comprising one or more active ingredients which show significant panthotenate synthetase inhibition in an assay according to claim
 17. 20. A nucleotide probe capable of specifically hybridizing to plant pantothenate synthetase gene or mRNA, wherein the probe comprises a contiguous portion of the coding sequence for a pantothenate synthetase from a plant at least 10 nucleotides in length.
 21. A method of producing a DNA molecule comprising a DNA portion encoding a protein having pantothenate synthetase activity comprising, a) preparing a nucleotide probe capable of specifically hybridizing to a plant pantothenate synthetase gene or mRNA, wherein the probe comprises a contiguous portion of the coding sequence for a pantothenate synthetase from a plant at least 10-nucleotides in length; b) probing for other pantothenate synthetase coding sequences in populations of cloned genomic DNA fragments or cDNA fragments from a chosen organism using the nucleotide probe prepared according to step a); and c) isolating a DNA molecule comprising a DNA portion encoding a protein having pantothenate synthetase activity.
 22. The use of a nucleotide probe according to claim 19 to amplify pantothenate synthetase coding sequences from a chosen organism via the process of polymeras chain reaction. 